Accumulators may be used to store a volume of fluid under pressure or absorb pressure shocks caused by a sudden pulse of fluid entering an hydraulic system. Examples are disclosed in GB 892 019 and GB 2 083 556-A. Such accumulators may contain a sealed moveable member such as a flexible diaphragm or piston with a compressible gas or mechanical spring on one side acting in opposition to the system fluid pressure on the other. Whilst the characteristics of a mechanical spring must be pre-selected at the outset to be compatible with the range of pressures likely to be encountered in the system, a gas spring has the advantage that its characteristics can be changed at any time by charging or releasing the gas pressure, as required.
EP 1 079 170 A2 discloses a gas spring accumulator comprising:
a housing provided with an inlet; and
a flexible diaphragm dividing the interior of the housing into a working chamber which is exposed to system pressure via the inlet, and a gas chamber;
wherein the housing is provided with a port which communicates with the gas chamber and to which an external pressure vessel is releasably attached.
One disadvantage of gas spring accumulators is that a large gas chamber may be required to store the charge. Such devices are often difficult to accommodate, and may also be subject to vigorous pressure testing requirements. Furthermore, there is usually no easy way of determining when the accumulator is charged to a pressure which is compatible with the system pressure, which may necessitate taking readings of the system pressure and the gas charge.
The present invention seeks to provide a new and inventive form of accumulator which is capable of operating at its maximum efficiency without having to manually charge the system to the required gas pressure.
A second aim is to provide an accumulator which is relatively compact and lightweight yet is capable of accommodating a large pressure charge when required.
A third aim is to provide an indication of the charge pressure without using additional pressure gauges.